3-projector set up that needs to alternate between single image and treating each projection area individually

I'm in the process of planning a show that would require three rear-projectors hooked up to one MacBook Pro. I've looked into the Matrox triplehead2go device for connecting them, so I intend to go that route; but my issue is that there would be moments during the show where the three projectors are showing different imagery (treating each surface individually), as well as times when all three are projecting a single moving image (one image split three ways). The content is linear, (though I anticipate having to manually trigger scenes to play), and would consist of .mov files composited in Aftereffects. I'm guessing that I would need to have a patch that would be conducive to this, and organize my videos so that some of them can be displayed as a single image over 3 projectors, and for the times that I need to treat each projection individually, there would probably have to be 3 separate videos triggered at once, which are being fed through each projector. Does this make sense? I'm sorry for confusing anyone. I just need to know what the best approach is for alternating between the two modes of projecting, and if anyone has any suggestions for how to build a patch that would facilitate this.

Thank you so much! Please let me know how to clarify further, if this is too confusing.

Personally I would use Projection Mapping (IzzyMap) (Drag a Projector inside your Scene, double click the icon of the Projector with the 'map' at the right side) to create the necassary mapping. I don't know or the Matrix will show himself as a 1920 x 1080 x 3 Output or as a 5760 x 1080 output, that will change the amount of Projector mappings.

After that we can create a simple Video Gate to actually decide to what Projection Mapping the signal is going and trigger that with our scenes.

Attached is a screenshot how to start. You check the movie size of the first movie player, if it is for example 5760px (3x1920) change the selector to the top projector actors that you have configured (mapper with double click) to spread one movie across three projectors with the same trigger impulse of the value true you can set a trigger value of 0 to set the bottom movie players to not play a movie. If the value is lower than 5760px then switch the selector to the projector actors at the bottom, they are not mapped in any way.

Sorry for only posting a picture I did the patch in the not yet public available 2.6 and you can't open it in 2.5.2, and you learn more if you do it yourself ;-)

@michel Ok, thanks--that's good to know! I have one more question: I was looking up the Matrox Triplehead2go and noticing that it costs over 200 dollars. Would you happen to know of an alternative that can be used to connect 3 hdmi projectors to a MacBook Pro 15" that will still be compatible with Isadora?

@michel I have 4 thunderbolts but no HDMI. I only have one thunderbolt to HDMI adapter, so 2 more would cost quite a bit as well--but still cheaper than the triple head, so might go that route instead.